1. Field of the Invention
The present invention relates generally to a capacity control valve for variably modulating a capacity or a pressure of a process fluid in a control chamber through a valve body which is connected with an operating rod. More particularly, the invention relates to a capacity control valve in which anti-abrasion capability of the operating rod in an opening or closing action of the valve body is improved and its slide resistance is decreased where the valve body is integrally attached to the operating rod.
2. Description of the Related Art
There have been known as a relative art 1 of the present invention capacity control valves for a variable displacement type swash plate compressor. In a capacity control valve of this kind, an operating rod mounting a valve body thereon is connected with a solenoid portion or a pressure sensitive device, thus the rod results in a long structure. The operating rod is also connected with a solenoid rod which is guided in a freely slidable manner through a bore inside a fixed iron core of a solenoid portion. Further, the capacity control valve accommodates the operating rod which is integrally connected with the solenoid rod of a large longitudinal length and a small radius.
A capacity control valve 100 shown in FIG. 5 is similar to the capacity control valve of the related art 1. Therefore the related art 1 is described through FIG. 5. A valve housing 105 in FIG. 5 has a through hole which axially extends therethrough. The through hole disposes a discharge valve hole 110C, suction valve hole 110D, a first guide hole 110E, and a second guide hole 110F therein. Also a valve chamber 111 is disposed between the discharge valve hole 110C and the suction valve hole 110D. Further, a first suction pressure passage 110B1 is arranged to communicate with the suction valve hole 110D. Also a discharge pressure passage 110A is arranged to communicate with the discharge valve hole 110C. Described at the bottom of the figure is a second suction pressure passage 110B2 which is arranged to communicate with the through bore.
In the valve housing 105, a first valve housing 105A and a second valve housing 105B are integrally connected with each other at their respective end portions by means of screw thread. A spring container 120 is formed within an end portion of the first valve housing 105A. An opening end of the spring container 120 is screw-engaged with a spring seat 122. A spring means 121 is disposed between the spring seat 122 and the operating rod 101, and a spring force of the spring means 121 is adjusted by rotating the screw thread of the spring seat 122. This spring means 121 provides the operating rod 101 with a resilient, urging force which is pointing upward, as indicated in the figure.
The through hole of the valve housing 105 contains the operating rod 101 therewithin. The operating rod 101 forms an integral construction which includes a first stopper 110E which slides relative to the first guide hole 110E, a valve body 101A which is disposed within a valve chamber 111, a second stopper 101F which slides relative to the second guide hole 110F, and a solenoid rod 101C which is fitted to a rod hole 132A of the fixed iron core 132 in a freely slidable manner. The valve body 101A has valve faces thereon and the respective valve faces disposed at both end faces of the valve body 101 are brought into contact with or lifted from the opposing valve seats of the valve housing 105 to adjust the opening degree of the discharge valve hole 110C and the suction valve hole 110D, respectively.
Displacement of the valve body 101A in opening direction of the discharge valve hole 110C allows the fluid of discharge pressure in the discharge pressure passage 110A to rigorously flow into a crank case pressure passage 110G. This, at the same time, creates a movement of the valve body 101A in closing direction of the suction valve hole 110D, which throttles the fluid of suction pressure of the first suction pressure passage 110B1 flowing into the crank case pressure passage 110G. The operating rod 101 integrally built with the valve body 101A makes a movement with the first stopper 101E sliding relative to the first guide hole 110E and with the second stopper 101F sliding relative to the second guide hole 110F. Further, the valve body 101A is brought into contact with or is lifted from the valve seat. For this reason, the valve body 101A as well as the first stopper 110E and the second stopper 101F must be hardened through heat treatment to prevent wear. Also the heat treated surfaces need to be finished by a grinding process.
A solenoid portion 130 is disposed at the other end of the valve housing 105. The solenoid portion 130 consists of a fixed iron core 131, a moveable iron core 132 and an electromagnetic coil 135. The moveable iron core 132 operates through an energization of the solenoid portion 130, which forces the solenoid rod 101C to move. Movement of the solenoid rod 101C is guided by the rod hole 132A of the fixed iron core 132. A portion of the fluid of suction pressure from the first suction pressure passage 110B1 is allowed to flow into a moveable iron core chamber 136 after passing through a clearance gap on the outer perimeter surface of the solenoid rod 101C. This equalizes the suction pressure Ps inside the moveable iron core chamber 136 and the suction pressure Ps of the suction pressure fluid flowing into the spring chamber 120 through the second suction pressure passage 110B2, both of which equally act on the operating rod from its both sides.
In a capacity control valve 100 of this kind, the valve body 101A opens and closes the discharge valve hole 110C and the suction valve hole 110D in mutually exclusive a manner as the result of an upward motion of the operating rod 101 which is created by an action force being proportional to the electric current given to the solenoid portion 130 and a reaction force of the spring means 121. The mutually exclusive control of the opening and closing of the discharge valve hole 110C and the suction valve hole 110D causes the fluid of discharge pressure Pd and the fluid of suction pressure Ps to flow into a crank case of a compressor for controlling a swash plate thereof wherein the compressor is not included in the figure.
The operating rod 101 of the capacity control valve 100 needs to be arranged to have a hard surface because the operating rod 101 is subject to sliding movement relative to the first guide hole 110E and the second guide hole 110F. A valve face of the valve body 101A also requires a hard surface because the valve face is brought into contact with a valve seat. Further, the first stopper 101E and the second stopper 101F are aligned with each other in a coaxial manner in order to reduce a slide friction. Also the valve face needs to be fabricated perpendicular to the axis of the operating rod 101. In order to do so, the operating rod 101 is machined by grinding after a heat treatment process. The operating rod 101, however, has a body of large longitudinal length and the heat treatment often causes an axial bending of the rod. In addition, a small diameter of the operating rod 101 imposes difficulty on the use of grinding process. In particular, a great difficulty resides in the grinding process of the valve face to arrange the valve face perpendicular to the rod axis. This may cause a deficiency of the operating rod 101 in that the operating rod 101 is no longer able to keep up with the spring force of the spring portion 121 or the electric current of the solenoid portion 130 when the spring portion 121 acts on the operating rod 101 or the solenoid portion 130 is energized through the modulation of the current. Therefore the control of the capacity control valve 100 affects operation of the compressor.
Problems remaining in the relative art 1 and relative art 2 are clarified in the following description. In the relative art 1 (for the relative art 2, corresponding members should be referred to in FIG. 5), the fixed iron core 132 is magnetic and iron powder contained in a fluid under suction pressure Ps is attracted to an inner surface of the magnetized bore before reaching the moveable iron core chamber 136 by passing through the clearance gaps in the second guide hole 110F and in the rod hole 132A of the fixed iron core 132. The attracted iron powder remains on the slide surface and causes abrasion of the inner surface of the bore as well as of the operating rod 101 during relative sliding movement. In particular, the iron powder deposited on the second guide hole 110F of the valve housing 105 causes a trouble on the operation of the operating rod 101 (connecting rod retainer in case of the relative art 2). Also iron powder and the like tend to be accumulated in a region close to the second stopper 101F of the rod hole 132A in the fixed iron core 132. The accumulated iron powder hampers the operation of the operating rod 101. If the solenoid rod 101C and the operating rod 101 are defined as separate members and their respective contact surfaces are brought into contact with each other, the iron powder accumulated in the region close to the second stopper 101F of the rod hole 132A in the fixed iron core 132 is introduced into an interface between the two contact surfaces of the solenoid rod 101C and the operating rod 101 as the operating rod 101 operates, which deteriorates the opening/closing performance of the valve body 101A. This causes the capacity control valve 100 to lose control over the fluid under the crank chamber pressure Pc.
In a capacity control valve of this kind, the following drawbacks remain due to the arrangement constructed as above. First, an operating rod of the capacity control valve requires a quenching process as heat treatment in order to increase hardness of the slide surface for preventing wear thereof. Such a heat treatment process, however, raises problems such as axial bending or strains. Therefore, this necessitates not only a polishing process of the heat treated surface after the original heat treatment process but also a re-grinding process in order to correct the axial bending. In addition, a small radius of the operating rod makes it difficult to apply a grinding process thereto. Further, the valve face also requires to be processed by grinding after heat treatment to ensure perpendicularity of the valve face with respect to the longitudinal axis. This grinding process is also demanding due to its necessity of machining in a perpendicular direction relative to the longitudinal axis, which increase a production cost.
Further, iron powders magnetized between the solenoid rod and the rod hole of the fixed iron core are attracted to the fixed iron core and makes the solenoid rod difficult to operate normally. Such contaminants like the iron powders or the like are hard to be gotten rid of because they are introduced in a source fluid to begin with. Also wear of the fixed iron core is tough to be avoided because of the limited availability of its material. As a result, the abrasion powders attracted to the rod hole make the solenoid rod difficult to operate under a normal condition.
The present invention is introduced to resolve the above mentioned problems. A primary technical goal which this invention tries to achieve is to prevent wear in sliding motion by hardening an operating rod and to achieve dimensional accuracy for the normal operation of the operating rod. Another goal is to decrease the production cost of the operating rod. Yet another goal is to ensure the normal operation of the operating rod by preventing impurities from being attracted to between the sliding surfaces of the rod hole of the fixed core and the solenoid rod.